The long range goal is to more fully understand the physiology of the pituitary folliculostellate (FS) cell. No unequivocal function has been demonstrated for these cells. The hypothesis to be tested is that FS cells affect anterior pituitary (AP) physiology by altering the local extra- or intracellular levels of 3', 5' cyclic adenosine monophosphate (cAMP) and Ca2+. Altered local levels of cAMP and Ca2+ then affect the rate of hormone secretion from secretory AP cells. The specific aims are to: 1) develop and validate an in vitro cell culture paradigm for rat FS cells, 2) describe the morphology and ultrastructure of FS cells in these cultures and analyze the patterns and nature of FS cell association with AP cells, 3) determine the effects of FS cells on hormone secretion from other AP cells and 4) elucidate the mechanisms by which FS cells might communicate with other FS cells and influence hormone secretion from AP cells. These aims will be achieved by developing monolayer cultures of FS cells on an extracellular matrix. Highly enriched populations of FS cells will be obtained by separation of monodispersed pituitary cells by unit gravity sedimentation. These cells will be used then to initiate the monolayer FS cell cultures. The monolayer cultures will be used for studies of cAMP production in basal and hormone-stimulated states. Intracellular Ca2+ mobilization will also be examined in these states with Quin 2 fluorescence. Cell-cell connections will be examined using a dye coupling model. Finally AP hormone (growth hormone, luteinizing hormone and prolactin) secretion from individual AP cells, either associated with FS cells or unassociated, will be examined with reverse hemolytic plaque assays for these hormones. The effects of FS cells on hormone secretion, secretagogue responsiveness and the spectrum of secretagogues to which AP cells respond will be investigated. These studies of FS cell physiology are likely to provide additional insight into the growth of the AP in fetal development and various neoplastic conditions.